Calculate the internal energy of 25.0 g of low-density oxygen gas (O2) at a temperature of 255 K.

To calculate the internal energy of a gas, you need to use the equation:

U = (3/2) * n * R * T

Where:
U is the internal energy
n is the number of moles of the gas
R is the ideal gas constant (8.314 J/(mol·K))
T is the temperature of the gas in Kelvin

To calculate the number of moles of the gas, you can use the equation:

n = mass / molar mass

Where:
mass is the mass of the gas
molar mass is the molar mass of the gas

Let's start by calculating the number of moles of oxygen gas (O2):

The molar mass of oxygen (O) is 16.00 g/mol, and since O2 has 2 oxygen atoms, the molar mass of O2 is 2 * 16.00 g/mol = 32.00 g/mol.

Now, we can calculate the number of moles:

n = 25.0 g / 32.00 g/mol = 0.78125 mol

Next, we can plug this value of n into the equation for internal energy:

U = (3/2) * n * R * T

U = (3/2) * 0.78125 mol * 8.314 J/(mol·K) * 255 K

Calculating the expression:

U ≈ 3.99 kJ

Therefore, the internal energy of 25.0 g of low-density oxygen gas at a temperature of 255 K is approximately 3.99 kJ.